Optical closure is essential for the determination of biogeochemical properties from ocean color remote sensing information. Mie scattering theory, a radiative transfer model, and a semi-analytical inversion algorithm were used to investigate the influence of particles and their properties on optical closure. Closure results were generally poor. Absorption coefficient (a(t)) inversions were more accurate for moderate particle size distribution slopes (3.50 < or = xi < or = 3.75). The degree of success in the derivation of the backscattering coefficient (b(bp)) was highest at moderate indices of refraction (1.15 < or = n(p) < or = 1.20) and high values of xi(> 3.75). Marked improvements in the estimates of b(bp) were enabled by a priori knowledge of bbp at one wavelength. At moderate values of n(p), derivations of a(t) and b(bp) were within 25% of Mie-modeled values when Gershun's relationship was used in combination with the semi-analytical algorithm.